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Our unique foundation leveling & house lifting process

Find out more about the Slabjack system below or contact us to find out more about our services including:

  • concrete foundation repairs
  • house foundation repairs
  • cracked foundation repairs
  • concrete floor repairs
  • basement & wall crack repairs.

 

The Slabjack System & Methodology

Step 1 - Property Assessment and Lift Planning

  • Record and document SJ initial floor levels
  • Assess & record building damage
    • Cracks in foundation, slab & cladding and identification of hinge points
    • Lintel, soffit and roof levels
    • Damage to internal linings
    • Thresholds – doors, windows & openings
  • Structural review
    • Thorough review of available documentation – Geotech, Structural engineering report, as built plans, etc.
    • Ferro scanning, to determine structural capacity of building elements and connections
  • Define and document building lift plan
    • Risk assessment – Structural, geotechnical, services, groundwater, etc
    • SJ stitch requirement (unreinforced concrete)– slabs, foundations, intertennancy walls, etc
    • Perimeter and internal lift points
    • Grout injection layout giving consideration to services & sanitary, penetrations, cracks, etc
    • Internal line / point load lift requirements – for firewalls, loadbearing walls and point loads

Step 2 - Lift Preparation

Lift Preparation

  • Site Induction and SSSP Implementation
    • All staff at SJ hold Site Safe BC Passports & SJ is finalising Appcon registration
    • SJ employs a third party safety consultant to perform regular site audits for continual improvement
  • Site & building markup
    • Markup site and building according to lift plan
  • Dig holes and prep for foundation lifting
    • Discrete holes are dug around the building for screw piles & lifting assemblies
  • Core drilling and prep for internal slab lifting
    • Dia 150 holes are drilled through slab
    • Discrete rapid set concrete pads are poured into holes to bind tailings & prevent jack bounce
  • Core drilling for grout injection
    • Dia 50 holes are drilled in a grid pattern for SJ cementitous grout injection
  • If required: Cutout access panels to lift internal line & point loads
    • The usual requirement is for a 600mm sq access hatch, however site specific requirements may vary

Step 3 - Install Hardware

  • Fit faceplates to foundation
  • Drive screw piles into the ground to set depths
    • This is done using the SJ guide system that fits to the faceplate to ensure accurate set position
  • Install Universal Lifting Brackets (T4ULB) and ancillary around perimeter
    • This includes a pile cap and mechanical locking system to prevent hydraulic settlement
  • Install Internal Lifting Brackets (T4ILB | Halo’s)
    • This can include a locking system also if deemed necessary
  • If required: Fit Stitching Plates and structural bolstering equipment
    • If the building has a fundamental lack of reinforcing (i.e unreinforced slab)
    • Where structural connections are substandard or non-existent (i.e. no slab to footing connection)
    • When there is considerable damage – cracking, lateral spread, etc.
  • If required: Install internal T4ULBs and Universal Lifting Beams (T4ULBeam)
    • For lifting firewalls, loadbearing walls & point loads

Step 4 - Level Building

  • This is a slow, considered and staged process
    • The levelling is carried out systematically by a SJ team
    • The perimeter of the building is levelled in gradual steps
    • Concurrent correction of the slab, firewalls, loadbearing walls and point loads
  • Continuous monitoring of the building structure
    • Monitoring cladding hinge points (obvious with brick veneer cladding)
    • Monitoring services – downpipes, gully traps, power cables, stormwater & sanitary sewer lines
  • Continuous monitoring of floor levels
  • Continuous monitoring of hydraulic load distribution
    • The pressure distribution during the lift relates directly to load distribution
    • Lift strategies are employed accordingly
  • The extent to which a building can reasonably be levelled is site specific
    • Each building is reviewed throughout the levelling process to ensure that the best outcome is achieved
    • This is dependent on monitoring feedback that indicates the building’s inherent structural limitations
    • I.e. Poorly cast slabs, innate out of level, renovations carried out post earthquake, etc

Step 5 - Grout Injection

  • Grout is site mixed & pumped
    • This minimises waste and maximises control
    • SJ cementitous grout consists of pre-bagged SJ mix, cement and specialist admixes
  • SJ Grouting is a low pressure process
    • Minimal grout pressure is applied to the ground or building
    • Slab drape can be removed by way of grout injection. This is done by mobilising a large area, though still at low pressure (typically <10bar at pump)
  • Working from the perimeter towards the middle
    • This ensures that the largest voids are filled first
    • Reduces slab spanning and load reduction of external jacks
    • Prevents introduction of voids
  • Grout hole centres are typically 2m apart
    • Grout travels from hole to hole ensuring that voids are completely filled
  • Continuous monitoring of floor levels & final level setting

Step 6 - Site cleanup, job completion & signoff

  • Remove hardware
    • Remove Universal Lifting Brackets (T4ULB) around perimeter & grouting of fixing holes
    • Removal of screw piles
    • Removal of internal lifting brackets (T4ILB | Halo’s)
    • If required: Removal of stitch plates, bolstering equipment and grouting of fixing holes
    • If required: Removal of internal T4ULBs and Universal Lifting Beams (T4ULBeam)
  • Site cleanup
    • Fill in holes and cleanup around the perimeter foundation
  • Waterproofing and filling of core holes
    • SJ uses certified waterproofing subcontractors for this
  • If required: Reinstate slab access hatches
    • Including repair of DPC, epoxied slab starters and mesh
  • Record and document SJ initial floor levels
  • Job review & signoff (record of acceptance)
    • Including provision of Documented Final Floor Levels and PS3

Find out more about all our slabjacking and mudjacking services by calling 0800 7522522 or requesting a free quote online!

Slabjacking NZ Ltd
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